Error reporting caused by the use of responsebodyadvice interface and its solution

One 、ResponseBodyAdvice Use

ResponseBodyAdvice Used before the return value is written to the response , take body Re encapsulation of content , Go straight to the code

1.1 CommonResponseDataAdvice

@Component
public class CommonResponseDataAdvice implements ResponseBodyAdvice<Object> {
    
    private static final String V_3_API_DOCS = "/v3/api-docs";
    private static final String SWAGGER_RESOURCES = "/swagger-resources";
    private static final String ADMIN_ACTUATOR = "/actuator";

    public boolean supports(MethodParameter methodParameter, Class<? extends HttpMessageConverter<?>> aClass) {
    
        if (methodParameter.getAnnotatedElement().isAnnotationPresent(IgnoreResponseAdvice.class)) {
    
            return false;
        } else {
    
            return !methodParameter.getMethod().isAnnotationPresent(IgnoreResponseAdvice.class);
        }
    }

    @Nullable
    public Object beforeBodyWrite(@Nullable Object o, MethodParameter methodParameter, MediaType mediaType, Class<? extends HttpMessageConverter<?>> aClass, ServerHttpRequest serverHttpRequest, ServerHttpResponse serverHttpResponse) {
    
        // Avoid being right swagger Of api The interface return value is encapsulated 
        if (((ServletServerHttpRequest) serverHttpRequest).getServletRequest().getRequestURI().equals(V_3_API_DOCS)) {
    
            return o;
        }
        if (((ServletServerHttpRequest) serverHttpRequest).getServletRequest().getRequestURI().contains(SWAGGER_RESOURCES)) {
    
            return o;
        }
        // Avoid being right actuator The monitoring interface of 
        if (((ServletServerHttpRequest) serverHttpRequest).getServletRequest().getRequestURI().contains(ADMIN_ACTUATOR)) {
    
            return o;
        }
        if (o instanceof Result) {
    
            return o;
        }
        return new Result<>(0, "",o);


    }
}

Key methods beforeBodyWrite, stay SpringMVC The main process has mentioned

It will be called , Thus, the return value is encapsulated into a custom Result Inside , It is convenient for the front end to uniformly process the status code .

Two 、 Error reporting and resolution

2.1 Integrate swagger Report errors

In integration swagger after , Always report an error , Interface documents can't come out , The following error message appears ：

Unable to render this definition
The provided definition does not specify a valid version field.
Please indicate a valid Swagger or OpenAPI version field. Supported version fields are swagger: “2.0” and those that match openapi: 3.0.n (for example, openapi: 3.0.0).

Baidu has been useless for a long time , Last check /v3/api-docs After the interface finds that the return value is encapsulated ,swagger The front end of cannot parse the custom structure , Result in an error .
Solution ： Determine the specific interface path without encapsulation

2.2 Interface directly returns String Type error

Define an interface

@GetMapping("/getUserName")
    @ApiOperation(" according to ID Get users ")
    public String getUserName() {
    
        return "username";
    }

Use Swagger Send a request

Wrong report , be supposed to Result Cannot be forced to String, There is no way but to find a solution from the source code , according to SpringMVC Main process , The key place is still here

Spring Provides 10 A message converter ,String stay Json In front of . call beforeBodyWrite After method

First match to the converter StringHttpMessageConverter, And will be body Encapsulated into Result type

StringHttpMessageConverter The generics of are String, Get into write After method

t The type is Result, A subclass of addDefaultHeaders What the method needs is String

Cause type strong conversion exception
Solution ： Interface return String Type , Use in advance Result encapsulation . Can't be in beforeBodyWrite Judgment is StringHttpMessageConverter No encapsulation , because StringHttpMessageConverter After the conversion, return to ,Json The converter will not be used .

@GetMapping("/getUserName")
    @ApiOperation(" according to ID Get users ")
    public Result<String> getUserName() {
    
        return new Result<>("username");
    }